The correct decreasing order of dipole moments for the molecules H ₂ O , NH ₃ , NF ₃ and BF ₃ is

Step-by-step solution

The dipole moment of a molecule depends on its geometry and the vector addition of bond dipoles and lone pair dipoles. BF ₃ has a symmetrical trigonal planar geometry, so the bond dipoles cancel out exactly, resulting in a net dipole moment of zero. In H ₂ O , the molecule is bent with two lone pairs. The highly polar O - H bonds and the two lone pairs strongly reinforce each other, giving it the highest dipole moment among the given molecules ( 1.85 D ). In NH ₃ , the lone pair orbital dipole is in the same direct